The present invention relates to papermaking fabrics and a method for making decorative and high bulk tissue. More particularly, the invention is directed toward patterned papermaking fabrics for visually enhancing, improving the texture, and adding a decorative designer signature to a fibrous web during papermaking, and the method of their use.
In the manufacture of paper products, particularly tissue products, it is generally desirable to provide an aesthetically pleasing final product with as much bulk as possible without compromising other product attributes, including softness, flexibility, absorbency, hand feel, and durability. However, most papermaking machines operating today utilize a process known as xe2x80x9cwet-pressingxe2x80x9d. In xe2x80x9cwet-pressingxe2x80x9d a large amount of water is removed from the newly-formed web of paper by mechanically pressing water out of the web in a pressure nip. A disadvantage of the pressing step is that it densifies the web, thereby decreasing the bulk and absorbency of the sheet. One problem encountered in the past by first wet web pressing and/or then dry embossing is the difficulty in obtaining a tissue basesheet with good functionality, such as absorbency and softness, in combination with a pleasant appearance. This wet-pressing step, while an effective dewatering means, compresses the web and causes a marked reduction in web thickness, thus reducing bulk. In addition, using embossing to apply signature designs to a dry web generally results in a paper product that is gritty to hand feel, stiffer at the pattern edges, and with decreased absorbency.
In the preferred through drying method, the wet web is formed by dewatering the papermaking furnish on a forming media, such as a forming fabric or wire. Then, the wet web is transferred to a permeable through-air-drying fabric around an open drum and non-compressively dried by passing hot air through the web while in intimate contact with the fabric. Throughdrying is a preferred method of drying a web because it avoids the compressive force of the dewatering step used in the conventional wet press method of tissue making. The resulting web optionally may be transferred to a Yankee dryer for creping. Because the web is substantially dry when transferred to the Yankee dryer, the Creped Through Air Dried (CTAD) process does not densify the sheet as much as the wet press process. A particularly preferred web is made using the Uncreped Through Air Dried (UCTAD) process which avoids pressing altogether and produces a substantially uniform density web.
Papermaking fabrics are well known in the art. Examples of papermaking fabrics are shown in Wendt et al. U.S. Pat. No. 5,672,248, Chiu et al. U.S. Pat. No. 5,429,686 and Johnson et al. U.S. Pat. No. 4,514,345, which are hereby incorporated by reference. The prior art through-air-drying (TAD) fabrics are woven and further include weaving a strand into the woven fabric to add a different plane or dimension to the TAD fabric. As an example, the Chiu patent basically describes a woven or mesh fabric which may have additionally woven into it a strand, or a plurality of strands, which lays in a different plane or dimension than the woven or mesh fabric into which it is woven. Further, Chiu discloses a sculptured top-face of the through-air-drying fabric which contacts the tissue sheet. A bottom face of the throughdrying fabric confronts the throughdryer. The sheet, when through air dried in intimate contact with the base fabric and sculpture layer, forms a pleasing, three dimensional uniform background texture in the resulting tissue. However, the uniform textured background lacks any distinct decorative signature.
As in Johnson, other fabrics may begin with a conventional non-sculptured woven or mesh fabric as a base over which a stencil may be laid and a polymer spread to fill the openings in the stencil. Essentially, the polymer is allowed to cure and excess polymer is washed from the area over the stencil. These fabrics are costly to produce and are wasteful due to the excess polymer that must be applied and washed off. In addition, the tissue formed lacks the textured background and its associated attributes. The present invention overcomes these limitations and others in the prior art.
It has now been discovered that certain TAD fabrics can impart significantly increased bulk, increased flexibility, visual aesthetics and a high absorbent capacity to the resulting paper product. The height, orientation, and arrangement of the resulting protrusions in the sheet due to the use of a three-dimensional through-air-drying fabric with a decorative pattern thereon provides increased bulk, flexibility, and visual aesthetics and absorbent capacity. All of these properties are desirable for products such as facial tissue, wet-wipes, bath tissue and paper towels or related personal care products, herein collectively referred to as tissue products. The tissue sheets made in accordance with this invention can be used for one-ply or multiple-ply tissue products.
The patterned fabric may be formed in a number of ways. In one aspect of an embodiment, a three-dimensional throughdrying fabric is used to mold a tissue sheet into a three dimensional pattern or shape. A polymeric strand is adhered onto the top face of a three-dimensional sculptured throughdrying fabric, resulting in a thread-like decorative pattern such that the uniform background texture of the top face is apparent where the decorative pattern formed by the polymeric strand is absent.
In an embodiment of the invention, the polymeric strand applied to the TAD fabric is co-planar with the three-dimensional top face.
In a further embodiment, the polymeric strand applied to the TAD fabric is raised in comparison the three-dimensional top face.
In yet a second aspect of the invention, the invention relates to a through-air-drying fabric for wet molding a tissue sheet into a three-dimensional pattern or shape by contacting a tissue sheet with a three-dimensional sculptured first face of a TAD fabric. A polymeric yarn is stitched into the three-dimensional TAD fabric forming a pattern such that the textured first surface is apparent where the pattern formed by the polymeric yarn is absent.
In another aspect of an embodiment, the polymeric yarn stitched into the TAD fabric is co-planar with the three-dimensional top face.
In another embodiment, the polymeric yarn stitched into the TAD fabric is raised in comparison with the three-dimensional top face.
One advantage of the present invention is the addition of visual aesthetics to a tissue product made with a TAD fabric without subsequent dry embossing.
In some embodiments, a further advantage of the invention is to provide a method for adding bulk and visual aesthetics to a tissue product by using a three-dimensional TAD fabric without having to change any other machine clothing, equipment, or critical process values.
The invention will be better understood in light of the attached drawings and detailed description of the invention.